Okay, here's the deal:
I'm looking for some NiMH batteries. I came across these Tenergy cells on eBay.
I've been reading around Endless-Sphere and am getting mixed reviews.
Apparently they don't do too well at high discharge rates, but all I want them for is a measly 200W skateboard motor. With the 20 D cells I'm looking at the discharge rate should be about or less than 1C (24 x 10 = 240 Whrs). In fact, it may be less than this. The motor, I suspect, is rarely, if ever, drawing 200 watts. The SLAs currently in there are providing me with an "actual" capacity of about 72 Whrs, and lasting around 20 minutes. This gives me an average rating of about 180 watts, and, because my sister's board is a little slower than mine, I'm almost constantly accelerating and decelerating. I wouldn't be surprised if the Tenergy batteries lasted nearly an hour and a half at full speed. I know the batteries end up being around 8Ah, which is still almost three times what I'm getting out of the crappy SLAs in there now.
Basically, all I need to know is this: Will the Tenergy brand D cell 10000mAh work for what I want to use them for? If not which cells will for a similar price?
Oh yeah: The suspension is crap. How do they hold up to vibration?
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Did you learn anymore about the batteries? I have been researching them as well (how I came across your post). It seems the the sub C size batteries are specialized for higher discharge rates of 35 to 40 amps while the D batteries are rated for about 15-16 amps. How this effects how things run - I am still learning that.
Some of the batteries that have been reported as good, I have not personally tried them yet, are Ener-G 4600, IB 4200, and the tenergy seem to be ok as well.
The D cells suck. They barely do 1C, and probably at the cost of a reduced life cycle. I do recall that their sub-Cs (a cell format DESIGNED for high discharge) did perform reasonably well, though they didn't seem to give their rated capacity. Most of their cells seemed to not live up to their rated capacity, actually. This was gleaned from old reports, and I don't know if they still fail to meet their rated capacity.
I decided to stick with lead until lithium becomes cheaper. I did a quick cost comparison, and discovered that a quality NiMH cell will cost you about as much than an A123 LiFePO4 cell. They'll cost you MORE than a eBay duct tape pack, but the jury is still out on those.
HCT at one point recommended Panasonic's cells. I specced them out and was favorably impressed, but you will pay a lot for them. $20 a D cell.
Basically, the D cells are pretty much unsuitable for electric drive applications. Cs will work fine, especially if you parallel them up, but will cost more. It's also good to have some head room. You don't always want to be pushing the batteries to their limit. Not good for them.
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I can't speak for the D cells, but I bought 50 AA cells and went through them. Most of them shorted out at about 15 amps a few were above that and 5 or so were under 10 amps. I set the really good ones and not so goods ones aside. I have a heated jacket that pulls about 6 amps at 12v and wanted to run it off AA cells. So I have two 8 pack batteries holders in parallel so each is supplying 3 amps each, the problem is the holders are made for like 2 amps max. The batteries handle the load fine but the packs get warm, but so does my jacket :) I tried 2 10 pack holders but then each was supplying about 4 amps and the wiring on the packs get to warm, and so does the jacket. I am thinking 2 packs of 7 cells would be perfect temp wise in the jacket or maybe I could go back to the 10 packs and use the pwm heater control, but that adds weight and bulk.